You can upgrade
an ESXi 5.0.x or update an ESXi 5.1 host directly to ESXi 5.1.x, and in most
cases, you can migrate an ESX 4.x or upgrade an ESXi 4.x host directly to ESXi
5.1.x.

The details and level of support
for an upgrade, migration, or update to ESXi 5.1 from version 4.x ESX and ESXi
hosts, and version 5.0.x and 5.1 ESXi hosts, depend on the host to be upgraded
and the upgrade method that you use.

The following ESX/ESXi 4.x, ESXi
5.0.x and ESXi 5.1 versions are supported for upgrade, migration, or update to
ESXi version 5.1.x.

■

ESX/ESXi 4.0.x (including
all released updates and patches)

■

ESX/ESXi 4.1.x (including
all released updates and patches)

■

ESXi 5.0.x (including all
released updates and patches)

■

ESXi 5.1

Supported Scenarios for
Upgrade, Migration, or Update to ESXi 5.1.x

Scenario for Upgrade, Migration, or Update to
ESXi 5.1.x

Support

3.x ESX and ESXi hosts

Not supported for direct
upgrade.

You must upgrade
version 3.x ESX and ESXi hosts to ESX or ESXi version 4.x before you can
upgrade them to ESXi 5.1.x. See the vSphere 4.x upgrade documentation.

Alternatively, you might
find it simpler and more cost effective to do a fresh installation of ESXi
5.1.x.

4.x ESX host that was upgraded from ESX 3.x
with a partition layout incompatible with ESXi 5.x

Not supported.

The VMFS partition
cannot be preserved. Upgrading or migration is possible only if there is at
most one VMFS partition on the disk that is being upgraded and the VMFS
partition must start after sector 1843200. Perform a fresh installation. To
keep virtual machines, migrate them to a different system.

In the upgrade script,
specify the particular disk to upgrade on the system. If the system cannot be
upgraded correctly because the partition table is incompatible, the installer
displays a warning and does not proceed. In this case, perform a fresh
installation. Upgrading or migration is possible only if there is at most one
VMFS partition on the disk that is being upgraded and the VMFS partition must
start after sector 1843200.

4.x ESX host on a SAN or SSD

Partially supported.

You can upgrade the host
as you would a normal ESX 4.x host, but no provisions will be made to optimize
the partitions on the disk. To optimize the partition scheme on the host,
perform a fresh installation.

The most likely reasons
for a missing Service Console are that the Service Console is corrupted or that
the VMFS volume is not available, which can occur if the VMFS was installed on
a SAN and the LUN is not accessible. In this case, on the disk selection screen
of the installer wizard, if you select a disk that has an existing ESX 4.x
installation, the wizard prompts you to perform a clean installation.

4.x ESX or ESXi host, asynchronously released
driver or other third-party customizations, interactive migration from CD or
DVD, scripted migration, or migration with vSphere Update Manager

Supported with ESXi
Image Builder CLI.

If a 4.x host contains
customizations, such as third-party VIBS or drivers, upgrading with the
standard VMware installer ISO will result in the loss of those customizations,
and possibly an unstable system. See
Upgrading Hosts That Have Third-Party Custom VIBs.
You can ESXi Image Builder CLI to create a customized ESXi installer ISO file
that includes the VIBs or drivers. See the information on Image Builder in the
vSphere Installation and Setup documentation.

5.0.x or 5.1 ESXi host, asynchronously released
driver or other third-party customizations, interactive upgrade from CD or DVD,
scripted upgrade, or upgrade with vSphere Update Manager